refactor : Improve frontend setup doc and locale error

[dai-dao]

Improve front-end setup for new users

---

1. Fix make file to check for node 22 instead of node 20, since installing node 20 doesn't work anymore
2. Fix i18next to ignore the regional part of the language code entirely, loading only the primary language (e.g., "en"). This helps remove this error from the logs which is annoying.

Can't locate /locale/us-EN/translation.json

3. Small refactors for the routes folder to use fastAPI defined status codes instead of explicitly using integers

---

#6633

[amanape]

Thank you for these changes!

[enyst]

@dai-dao Linting is failing and the automated lint fails too, could you take a look?

[dai-dao]

@enyst it's fixed ready to merge

[enyst]

Thank you!